1. No
2. Good
3. No
4. Yes
SG Commonwealth and SG Grousemoor come both in tins and bulk ( Commonwealth also comes in 250g foil pouches in little boxes for easier storage than the pound-in-many-jars ). Being that it comes in from the UK, sometimes availability can be spotty from one place or another ( bulk but no tins and viceversa ).
I've only been smoking the pipe for 2 years so I haven't had a problem with stuff disappearing from production and/or market.
As for tin-only blends that are lovely in my book : Peterson Flakes ( Uni and Irish ), Erinmore Flake, Balkan Sasieni ( even though some say it's just tinned PS Balkan Supreme :mrgreen: ) and GLP Westminster ( even though it comes in 1 lb cans beside the 2 oz and 8 oz, it's still not "in a bag sold by the ounce" )